Permanent Wave Chemistry
A permanent wave (perm) restructures the disulfide bonds in the cortex of the hair to create a new wave or curl pattern. The process has two chemical steps:
- Reduction (waving lotion): The reducing agent breaks the disulfide bonds that hold the hair's natural shape. The hair is wrapped around rods to establish the new curl pattern. The hair takes the shape of the rod while in this softened state.
- Oxidation (neutralizer): The neutralizer (usually hydrogen peroxide or sodium bromate) stops the reducing action and rebuilds the disulfide bonds in the new curl shape. This step makes the wave permanent.
Types of Perm Solutions
| Type | Active Ingredient | pH | Best For |
|---|---|---|---|
| Alkaline (cold wave) | Ammonium thioglycolate (ATG) | 9.0 to 9.6 | Resistant, coarse, or healthy hair. Faster processing. Does not require heat. |
| True acid wave | Glyceryl monothioglycolate (GMTG) | 4.5 to 7.0 | Sensitized, damaged, or fine hair. Requires heat (endothermic). Gentlest result, slowest processing. |
| Acid-balanced wave | Glyceryl monothioglycolate (GMTG) | 7.8 to 8.2 | Color-treated or fine hair. Does not require heat. Faster than true acid wave. Firmer curl. |
The active ingredient in alkaline (cold wave) perms is ammonium thioglycolate. Acid perms use glyceryl monothioglycolate. Both are thio-based reducing agents, but their pH and processing method differ significantly.
Hair Relaxers
Relaxers permanently straighten the hair by breaking and reforming disulfide bonds, similar to perms. The two main types have very different chemistry and are never interchangeable.
Sodium Hydroxide (Lye) Relaxer
- Active ingredient: sodium hydroxide (NaOH)
- pH: 12 to 14 (extremely alkaline)
- Also called: lye relaxer or caustic relaxer
- Results: very straight, silky, but more damaging if misused
- Must not overlap onto previously relaxed hair (causes breakage)
Guanidine (No-Lye) Relaxer
- Active ingredient: guanidine hydroxide (formed by mixing calcium hydroxide + guanidine carbonate)
- pH: 9 to 11
- Gentler on the scalp. Marketed as "no-lye" for home use.
- Can cause calcium buildup on the hair shaft over time, leading to dryness and brittleness
Never apply sodium hydroxide relaxer on top of a guanidine (no-lye) relaxer, or vice versa, without a thorough strand test first. Mixing incompatible relaxer systems can cause severe breakage or chemical burns. Always take a complete chemical history from the client.
Required Tests Before Chemical Services
| Test | Purpose | When to Perform |
|---|---|---|
| Patch test (skin test) | Check for allergic reaction to chemicals | 24 to 48 hours before any chemical service involving oxidative color |
| Strand test | Check processing time, color result, and hair integrity | Before applying any chemical service to the full head |
| Porosity test | Assess how quickly hair absorbs and releases moisture | Before perms, relaxers, and color services |
| Elasticity test | Assess the hair's ability to stretch without breaking | Before any chemical service, especially on damaged hair |
Hair with low elasticity breaks when stretched rather than springing back. Do not perform a perm or relaxer on hair with poor elasticity without a conditioning treatment first. Proceeding anyway is a common cause of breakage and exam test questions about contraindications.